Start working on a branch where FFmpeg is not copied, patched and carved to be built with automake but instead imported inline and built using its own build system. This is an import of a slightly modified FFmpeg current tree. xine-lib builds, install and run fine with it, but there are of course plenty of things that needs to be fixed before it can even be considered for a 1.2.x series. Work will continue in the next days of course.

CVS patchset: 8397
CVS date: 2006/12/02 01:19:48

1 files changed, 158 insertions, 0 deletions

diff --git a/contrib/ffmpeg/doc/optimization.txt b/contrib/ffmpeg/doc/optimization.txt
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+optimization Tips (for libavcodec):
+
+What to optimize:
+If you plan to do non-x86 architecture specific optimizations (SIMD normally),
+then take a look in the i386/ directory, as most important functions are
+already optimized for MMX.
+
+If you want to do x86 optimizations then you can either try to finetune the
+stuff in the i386 directory or find some other functions in the C source to
+optimize, but there aren't many left.
+
+Understanding these overoptimized functions:
+As many functions tend to be a bit difficult to understand because
+of optimizations, it can be hard to optimize them further, or write
+architecture-specific versions. It is recommened to look at older
+revisions of the interesting files (for a web frontend try ViewVC at
+http://svn.mplayerhq.hu/ffmpeg/trunk/).
+Alternatively, look into the other architecture-specific versions in
+the i386/, ppc/, alpha/ subdirectories. Even if you don't exactly
+comprehend the instructions, it could help understanding the functions
+and how they can be optimized.
+
+NOTE: If you still don't understand some function, ask at our mailing list!!!
+(http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel)
+
+
+
+WTF is that function good for ....:
+The primary purpose of that list is to avoid wasting time to optimize functions
+which are rarely used
+
+put(_no_rnd)_pixels{,_x2,_y2,_xy2}
+    Used in motion compensation (en/decoding).
+
+avg_pixels{,_x2,_y2,_xy2}
+    Used in motion compensation of B-frames.
+    These are less important than the put*pixels functions.
+
+avg_no_rnd_pixels*
+    unused
+
+pix_abs16x16{,_x2,_y2,_xy2}
+    Used in motion estimation (encoding) with SAD.
+
+pix_abs8x8{,_x2,_y2,_xy2}
+    Used in motion estimation (encoding) with SAD of MPEG-4 4MV only.
+    These are less important than the pix_abs16x16* functions.
+
+put_mspel8_mc* / wmv2_mspel8*
+    Used only in WMV2.
+    it is not recommended that you waste your time with these, as WMV2
+    is an ugly and relatively useless codec.
+
+mpeg4_qpel* / *qpel_mc*
+    Used in MPEG-4 qpel motion compensation (encoding & decoding).
+    The qpel8 functions are used only for 4mv,
+    the avg_* functions are used only for B-frames.
+    Optimizing them should have a significant impact on qpel
+    encoding & decoding.
+
+qpel{8,16}_mc??_old_c / *pixels{8,16}_l4
+    Just used to work around a bug in an old libavcodec encoder version.
+    Don't optimize them.
+
+tpel_mc_func {put,avg}_tpel_pixels_tab
+    Used only for SVQ3, so only optimize them if you need fast SVQ3 decoding.
+
+add_bytes/diff_bytes
+    For huffyuv only, optimize if you want a faster ffhuffyuv codec.
+
+get_pixels / diff_pixels
+    Used for encoding, easy.
+
+clear_blocks
+    easiest to optimize
+
+gmc
+    Used for MPEG-4 gmc.
+    Optimizing this should have a significant effect on the gmc decoding
+    speed but it's very likely impossible to write in SIMD.
+
+gmc1
+    Used for chroma blocks in MPEG-4 gmc with 1 warp point
+    (there are 4 luma & 2 chroma blocks per macroblock, so
+    only 1/3 of the gmc blocks use this, the other 2/3
+    use the normal put_pixel* code, but only if there is
+    just 1 warp point).
+    Note: DivX5 gmc always uses just 1 warp point.
+
+pix_sum
+    Used for encoding.
+
+hadamard8_diff / sse / sad == pix_norm1 / dct_sad / quant_psnr / rd / bit
+    Specific compare functions used in encoding, it depends upon the
+    command line switches which of these are used.
+    Don't waste your time with dct_sad & quant_psnr, they aren't
+    really useful.
+
+put_pixels_clamped / add_pixels_clamped
+    Used for en/decoding in the IDCT, easy.
+    Note, some optimized IDCTs have the add/put clamped code included and
+    then put_pixels_clamped / add_pixels_clamped will be unused.
+
+idct/fdct
+    idct (encoding & decoding)
+    fdct (encoding)
+    difficult to optimize
+
+dct_quantize_trellis
+    Used for encoding with trellis quantization.
+    difficult to optimize
+
+dct_quantize
+    Used for encoding.
+
+dct_unquantize_mpeg1
+    Used in MPEG-1 en/decoding.
+
+dct_unquantize_mpeg2
+    Used in MPEG-2 en/decoding.
+
+dct_unquantize_h263
+    Used in MPEG-4/H.263 en/decoding.
+
+FIXME remaining functions?
+BTW, most of these functions are in dsputil.c/.h, some are in mpegvideo.c/.h.
+
+
+
+Alignment:
+Some instructions on some architectures have strict alignment restrictions,
+for example most SSE/SSE2 instructions on x86.
+The minimum guaranteed alignment is written in the .h files, for example:
+    void (*put_pixels_clamped)(const DCTELEM *block/*align 16*/, UINT8 *pixels/*align 8*/, int line_size);
+
+
+
+Links:
+http://www.aggregate.org/MAGIC/
+
+x86-specific:
+http://developer.intel.com/design/pentium4/manuals/248966.htm
+
+The IA-32 Intel Architecture Software Developer's Manual, Volume 2:
+Instruction Set Reference
+http://developer.intel.com/design/pentium4/manuals/245471.htm
+
+http://www.agner.org/assem/
+
+AMD Athlon Processor x86 Code Optimization Guide:
+http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/22007.pdf
+
+GCC asm links:
+official doc but quite ugly
+http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
+
+a bit old (note "+" is valid for input-output, even though the next disagrees)
+http://www.cs.virginia.edu/~clc5q/gcc-inline-asm.pdf